The homepage contains a Layer Control button for viewing different map layers. The layers cannot be edited but are intended to provide additional visualization while discovering data. Click here to learn how to add a GeoJSON layer from your local computer. Currently, there are four layers to choose from:
- USGS Stream Gages
- ESRI Hydrology
- ESRI HUC
- USGS LandCover 2011
To Select a layer, simply click on the Layer Control button shown below to view the list of layers.
Click on a layer of interest such as the USGS Stream Gages layer as shown below.
USGS Stream Gages
The USGS Stream Gage layer provides real-time streamflow compared to historical streamflow for the day of the year. The real-time information generally is updated on an hourly basis. The layer contains more than 3,000 long-term (30 years or more) USGS streamgages; uses colors to represent streamflow conditions compared to historical streamflow; and features a point-and-click interface allowing users to retrieve real-time streamflow conditions as shown below. The USGS Stream Gage layer was added from http://waterwatch.usgs.gov/index.php?id=real&sid=w__kml.
As shown below, the Esri Hydro layer shows relative flow of rivers of the world. Stream symbols of the same thickness and color represent roughly the same annual flow volume. As you zoom in more rivers will appear. This layer was added from: http://hydrology.esri.com/arcgis/rest/services/WorldHydroReferenceOverlay/MapServer/layers. For more information, visit http://resources.arcgis.com/en/communities/hydro/01vn0000001t000000.htm.
As shown below, the United States Geological Survey (USGS) Hydrologic Unit Code (HUC) map layer shows the National Watershed Boundary Dataset (WBD). It defines the perimeter of drainage areas formed by the terrain and other landscape characteristics. The United States is divided and sub-divided into successively smaller hydrologic units which are classified into four levels: regions, sub-regions, accounting units, and cataloging units. The HUC layer shows the United States Geological Survey (USGS) Hydrologic Unit Codes (HUC) consisting of 6 digits based on the four levels of classification in the hydrologic unit system. This layer was added from: http://services.nationalmap.gov/arcgis/rest/services/nhd/MapServer. For more information on HUCs, visit: http://water.usgs.gov/GIS/huc.html
USGS Landcover 2011
The USGS LandCover 2011 layer, shown below, contains the National Land Cover Database classification schemes based primarily on Landsat data along with ancillary data sources, such as topography, census and agricultural statistics, soil characteristics, wetlands, and other land cover maps. The layer was added from http://raster.nationalmap.gov/arcgis/rest/services/LandCover/USGS_EROS_LandCover_NLCD/MapServer.
To access the legend for this layer, simply click on the LEGENDS tab of the toolbar as shown below.